It can be frustrating to find out that Gmail is delivering the email you send to the spam folder. While we do everything possible to prevent this on our side by maintaining tight control over our network and what we allow to exit it, there is only so much that can be done before we have to hand this problem over to you. We can gladly share what we’ve learned, and hope that this helps you.
You do your best by making sure that you get a 10 out of 10 score from mail-tester.com. It’s simple: Go to mail-tester.com, copy the email address given to you, send an email to it, wait a few seconds, then click the button to check your score. We can’t help your content or domain reputation, but your DNS can get a 10 out of 10 by using our DNS tutorials.
It can do wonders to simply click “Not spam” in Gmail. Many of their filters are user trained, and it’s entirely possible that your recipients did the opposite at some point and reported your email as spam. It’s not always “the” solution, but it can help.
Google offers you a way to get insight into your domain’s activity with Gmail. Take the opportunity they give you: Get started with Postmaster Tools – Gmail Help (google.com)
The most clear communication you are going to get from Google is right in front of you, don’t skip a word of it: Prevent mail to Gmail users from being blocked or sent to spam – Gmail Help (google.com)